In recent years, in ultrasound 2-dimensional (2D) array probes, etc., electronic circuits have been embedded in a probe head in order to perform generation of the shape of transmitter pulses, and amplification of received echoes (received signals)/partial beamforming. An ultrasound diagnostic apparatus using such an ultrasound 2D array probe is described, for example, in Japanese Unexamined Patent Application Publication No. 2007-167445.
In an ultrasound diagnostic apparatus body to which such an ultrasound probe is connected via a probe connector, ultrasound echo signals subjected to reception delay and adding processing, are amplified by a unit preamplifier group. The amplified ultrasound echo signals are matched for timing in a reception delay adding circuit, detected in a signal-processing part in order to extract an envelope, and a coordinate transform is performed in an image-processing part, subjected to appropriate processing for the image display, and displayed on a display part. With this, form information regarding the inside of the object to be observed is displayed in real time.
Configurations of a conventional ultrasound 2D array probe and ultrasound diagnostic apparatus are described with reference to FIG. 9 and FIG. 10. FIG. 9 is a functional block diagram illustrating the configuration of a general ultrasound diagnostic apparatus. FIG. 10 is a block diagram of a channel control circuit in the conventional ultrasound 2D array probe.
An ultrasound vibrator group 102 is comprised, for example, by being aligned in arrays of N M, and sends and receives ultrasound to/from an object to be observed O (for example, heart). A pulsar group 101 is connected to the ultrasound vibrator group 102, and drives the ultrasound vibrator group 102 in accordance with different timings generated in a control circuit within a probe handle 100 in order to generate ultrasound beams having predetermined directionality. With this, the ultrasound beams are irradiated towards the object to be observed O from the ultrasound vibrator group 102 in accordance with electrical signals from the pulsar group 101.
The ultrasound beams sent from the ultrasound vibrator group 102 reflect, in response to structures and movements within the object to be observed O, at interfaces with different acoustic impedance such as boundaries, etc., of structural objects within the object to be observed O. A preamplifier group 103 performs low noise amplification or buffering, etc. in order to adequately transmit the imperceptible ultrasound echo signals that are received by the ultrasound vibrator group 102. A channel control circuit 104 provides, by a sub-array reception beamformer group 1041 that is embedded (see FIG. 10), the output signals from the aforementioned plurality of preamplifier groups 103 as one group with a delay time, adds these signals by an adder 1042 that is embedded (see FIG. 10), and outputs the resultant signals to the ultrasound diagnostic apparatus body. With this, the number of output signal lines from the ultrasound probe 1 can be reduced. In other words, the number of probe cables 11 is reduced.
The control circuit within the probe handle 100 is to control operations of the aforementioned pulsar group 101, preamplifier group 103, and channel control circuit 104. The preamplifier group 103 is configured such that it can individually set up operating conditions such as a bias current, etc. with control signals from this control circuit within the probe handle 100.
The probe handle 10 and the probe connector 12 are connected by the probe cable 11 as described above. The inside of the probe connector 12 is configured with an electronic circuit group 121 consisting of a plurality of electronic circuits, and a control circuit within the probe connector 120. The above electronic circuit group 121 performs additional processing such as amplification, buffering, and adjustment of bandwidth, as necessary, on ultrasound echo signals.
Moreover, the control circuit within the probe connector 120 is for controlling operation of the above electronic circuit group 121 and for generating control signals to be transmitted to the control circuit within the probe handle 100 based on control signals to be transmitted from an ultrasound diagnostic apparatus body 2 described later.
The ultrasound diagnostic apparatus body 2 is configured with a body preamplifier group 240, a body reception delay adding circuit 241, a signal-processing part 25, an image-processing part 26, a display part 27, a body transmission delay circuit 220, a body pulsar group 221, a body control circuit 21, and an operating panel 20.
In the body preamplifier group 240, ultrasound echo signals subjected to first reception delay adding processing are amplified in a group of several channels in the ultrasound probe 1. These amplified ultrasound echo signals are matched for timing in the body reception delay adding circuit 241. The above ultrasound signals are then detected in the signal-processing part 25, and an envelope is extracted.
In addition, after coordinate transformation is performed on this extracted envelope according to a cross-section of the object to be observed O, or appropriate gradation processing, etc. for image display is subjected in the image-processing part 26, it is displayed on the display part 27. With this, form information inside the object to be observed is displayed on the display part 27 in real time as shown in FIG. 11.
Moreover, the body control circuit 21 controls operation of each processing part within the ultrasound diagnostic apparatus body 2, and transmits control information to the control circuit 120 within the probe connector of the probe connector 12. The operating panel 20 is an input part for an operator to perform operation to input or select information in a case in which a continuous wave Doppler mode capable of beam steering is performed, etc. as an operating mode.
Furthermore, the body transmission delay circuit 220 and the body pulsar group 221 are operated when the ultrasound probe does not embed any electronic circuits, i.e., when a regular probe in which an ultrasound diagnostic apparatus body 2 drives an ultrasound vibrator group 102 is connected, and generally, they are configured to be built in the ultrasound diagnostic apparatus body 2, but they are not necessary.
As the operating mode of the ultrasound diagnostic apparatus described above, a continuous wave Doppler (hereinafter referred to as “SCW”) mode that is used for measurement of a blood flow rate, etc. is known. The SCW mode divides the ultrasound vibrator group aligned in arrays of N M into a Region B that sends ultrasound and a Region A that receives ultrasound as shown in FIG. 10 to operate, and with this, ultrasound can be continuously sent and received.
At the time of operating in the SCW mode, when transmission and reception of ultrasound of center frequency f0 are performed on blood flow within the object to be observed, the frequency of the ultrasound beams receives Doppler shift frequency fd proportional to the blood flow rate due to the moving blood cell, and ultrasound echoes of f0+fd is received. Therefore, by detecting the Doppler shift frequency fd and by displaying temporal changes, blood flow rate information can be displayed as a Doppler image as shown in FIG. 12.
Moreover, at that time, by mapping two-dimensionally the detected Doppler shift frequency fd, by performing appropriate color transformation, and by displaying it by superimposing over the foregoing ultrasound image, an image inside the object to be observed including the blood flow rate information can be displayed in real time as a color Doppler image (not shown).
In recent years, ultrasound 2D array vibrators have been used for an ultrasound probe, the number of vibrators has increased to several thousands, and the individual size has become very small. In this case, when the probe is directly connected to an ultrasound diagnostic apparatus, because a substantial number of cables is required, the cables as a whole become thick, affecting the operation, and causing difficulty in transmitting high-quality ultrasound echoes that are received by minute vibrators.
Therefore, in the case of ultrasound 2D arrays, etc., the number of signal lines that are input to an ultrasound diagnostic apparatus is often reduced by mounting electronic circuits such as a transmitting circuit and a receiving circuit onto an ultrasound probe, by efficiently amplifying received weak ultrasound echoes, and by performing partial reception beamforming on each unit of several vibrators to be added.
In the SCW mode, in order to amplify extremely weak Doppler signals superimposed on clutter (for example, reflected waves from the cardiac wall) with large amplitude that is detected on ultrasound beams, a wider dynamic range compared to the case of obtaining a normal B mode image is required.
However, the beamformer embedded in the ultrasound probe cannot take a wide dynamic range due to restrictions of electric power to be supplied, etc. This is because it is necessary to supply high electric power to the beamformer in order to secure a sufficient dynamic range; however, an increase of electric power involves heat generation. Because an ultrasound probe is used in contact with a subject, it is necessary to suppress this heat generation, and high electric power cannot be supplied.
Therefore, the conventional ultrasound probe having a reception beamformer cannot truly amplify weak signal components of the SCW due to the abovementioned restriction of the beamformer, and in the case of operating in the SCW mode, output signals cannot be added for each unit of several ultrasound vibrators to output to the ultrasound diagnostic apparatus body. With this, in the conventional ultrasound probe, the number of signal lines within the probe cables connecting the ultrasound probe to the ultrasound diagnostic apparatus body cannot be reduced, and the probe cables had to be made thick.